Surge problem at speed
when I accelerate heavily it sputters kinda like it is not firing correctly. At speed on the highway it will surge periodically, almost like it missfires, then it is fine. Literally just a quick misstep, then all is good. It seems to do this less at 70 miles an hour, which is about 3k on the tach.
You're mixing me up;
I see three problems right?
1) "when I accelerate heavily it sputters kinda like it is not firing correctly."
2) At speed on the highway it will surge periodically,
3) almost like it missfires, then it is fine. Literally just a quick misstep, then all is good.
4) seems to do this less at 70 miles an hour, which is about 3k on the tach
My guess is your plugs are overheating, and/or your coil is weak, AND on the low-speed circuit, yur a lil lean or running retarded low-speed AND cruise-timing.
Start by inspecting the plugs.
If I'm right, they will be almost pure white with lil patches of dark glaze on them. If they're not as described, I'm just wrong. lol.
But before you do anything, defeat the vacuum advance, and put a strobe-lite on it, then slowly rev it up while watching the timing mark on the balancer. You should see that it moves smoothly (
see note 2)beginning at about 1000 rpm and finishing at 3600rpm or maybe a lil less.
Then re-install the vacuum line to the SPARKPORT, and repeat,looking for same smoothness. Rev it to your cruise-rpm of ~3000, and your engine will be wanting about 48 degrees of cruise-timing there. See whatchagot.
Next, with the light still on it, rev it up to about 1800, and hold it there, Then with the light strobing, whack the throttle open, while watching the strobe. If the strobe hesitates, guess what, your coil failed to keep up. You will have to figure out why.
Finally;
With the transfer-slot to idle-discharge port ratio synced up; (
see note 1)
Clamp the power brake booster hose off, and make sure the PCV is working properly, and is plumbed correctly to just under the primary blades. Re-install the Vacuum advance if off. Next rev it up to ~2200 and put the throttle up on the nearest fast-idle step. Next, adjust the mixture screws for highest rpm. While there, check the timing. Your engine will like 40 to 45 degrees, but good luck giving her that much. Make a note of what yours has.
Return the engine to idle. Note the rpm, then, unclamp the booster hose and note any change in rpm. A momentary dip is normal, but it should come right back into line in just a few seconds. If it does not, then it is leaking air and you will have to fix that.
Next clamp off the fuel supply line, and wait.
A) After maybe 30 seconds, if the fuel level is about right, the rpm will start to rise, reach a plateau, hover there for a few seconds, then rapidly decline
B) If the level is too low, the rpm will start to fall immediately
C) If the level is too high, the rpm will start to rise almost immediately, and climb and climb for a long time, before turning around.
As soon as the rpm starts to drop, unclamp the fuel line and let the idle-rpm stabilize.
If your engine reacts as at B or C, then you will have to check the fuel level in the bowls.
HOWEVER,
If your Transfer port sync is out to lunch you will have to back up the bus and get that right first. Then start over.
Note 1
At idle, your carb is supposed to be spewing fuel from exactly two places only, namely; the transfer slots and the idle discharge ports. If your throttle blades are too far up the transfer slots, you will have to take fuel away using the ports. If your blades are not far enough up the transfers, you will have to crank the mixture screws out towards rich until you run out of adjustability.
The ideal place will have the mixture screws open to about 50% of their working range.
So set them to 50%. Then open or close the throttle blades to supply the balance of the fuel. If your idle-rpm gets wonky, you will have to change the timing to bring it back into a reasonable place. And then you will have to fine-tune the throttle blades again.
You will know when the sync is right by the following;
1) the idle rpm is in a window of about 650 in gear, no more than 100 rpm higher in neutral.
2) the engine does not want to stall on the Neutral to Drive shift, nor bang into gear.
3) freedom from a tip-in sag. That us to say, when you apply throttle GENTLY from idle, in gear, to take off gently; the car does not momentarily hesitate.
4) with the secondaries closed up tight but NOT sticking, and engine at idle, she should be slightly rich. Prove it by slowly restricting the airhorn. If the rpm flares up, she is lean.
You didn't mention having a cam so I'll skip that.
With a factory cam, this will require an idle timing of about 8 to 10, no more than 12 degrees. I would start on the low end.
When yur done, your power-timing needs to be in a range that does not cause detonation. A suggested starting point for a stock-type engine is 34* at 3400 rpm; with the Vcan defeated.
Note 2
If the strobe jumps around wildly from retard to advance AND she drops sparks; then
if you have a magnetic pick-up, the polarity is reversed.
If the strobe drops sparks only, check your reluctor gap.
Oh I almost forgot, make sure your fuel-tank vent is working.
